Bacteriological and physico-chemical quality of water from various sources in Samburu District and efficacy of selected plant products in water purification
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Limited access to safe drinking water and information on water quality in sparsely populated arid and semi-arid regions has contributed to frequent outbreaks of diarheal disease. There is therefore urgent need to determine the bacteriological and physico-chemical quality of water in various sources in these regions. This study was undertaken in order to determine water quality in Wamba Division of Samburu District and to asses the efficacy of plant extracts in purifying water. Bacteriological analyses was carried out using multiple tube fermentation technique and heterotrophic plate counts technique, while physicochemical analyses were carried out using standard methods. Qualitative bacterial determination confirmed the presence of thermotolerant eoliforms, Shigella and Salmonella spp. in most water samples examined. The same samples frequently recorded high levels of turbidity (range,S to 6100 NTU), alkalinity (range, 20 to 1577 mg L-! CaC03) and low salinity (range, 0 to 0.2 ppt). Faecal coliform load in dry river bed wells (mean 471.63) was higher than in the other categories of water sources (dams, rivers, springs and tap water). This study also found that the boreholes had the highest mean conductivity (830.8 )lS em") while wells had the widest range (4.6 to 5940.0). High levels of conductivity in water from groundwater sources can be attributed to the long period of contact between the water and mineral sources. Water treatment with alum, sodium hypochlorite and extracts from Boscia coriacea Pax. Maerua decumbens (Brogn.) Dewolf roots and Moringa oleifera Lam. seeds resulted in a varied reduction of bacterial and sediment loads of the water samples. Overall, all the treatments were found to be effective in reducing bacteria and sediment load in water samples collected from various sources, except for some unidentified residual bacteria that resisted the disinfection properties of plant extracts. Changes in the percentage load of heterotrophic plate counts (HPC) among the treatments used differed significantly (P < 0.05, DF = 5). Overall mean percentage change in HPC were 26.51, 46.00, 30.20 and 14.50 for M Oleifera Lam., M decumbens, B. coriacea and the control respectively compared to 74.76 and 90.95 in the case of alum and sodium hypochlorite in the same order. These values indicate that changes in bacterial density during water treatment may be due to loss of viability or alteration in eulturability. Results obtained in this study further indicated that there was no significant difference in water turbidity reduction (P < 0.05) by M oleifera, M decumbens and B. coriacea. Both B. coriacea and M decumbens chelants resulted in a high removal of the initial turbidity by 50.36 % and 43.87 % respectively during 30 minute treatment period while M oleifera were 40.53 %. As such the three species can be considered potentially useful chelants, and should be subjected to further study. During this study, it was noted that, plant extracts changed the water pH. This observation suggests that pH change possibly plays a vital role in inactivating bacteria in water. Bacteriological water quality analyses revealed that water from most sources had bacterial loads that exceeded the WHO value/guidelines for drinking water. Isolated species of E. coli, Salmonella and Shigella spp from water samples also showed varied antibacterial sensitivity to crude plant water extracts. This study therefore concludes that water from most sources is contaminated and must therefore be treated before consumption. It is recommended that further studies be conducted to identify the mechanism and active ingredients present in the plant extracts responsible for reducing sediment and bacterial load in water and how their efficacy is affected by the physico-chemical properties of water.